This invention relates to a new type of orifice plate for use in bubble-driven ink jet print heads and a method of manufacture.
The background with regard to bubble-driven ink jet printing is adequately represented by U.S. application Ser. No. 292,841 now abandoned by Vaught, et al., assigned to Hewlett-Packard Company, and by the following U.S. patents assigned to Canon Kabushiki Kaisha, Tokyo, Japan: U.S. Pat. Nos. 4,243,994; 4,296,421; 4,251,824; 4,313,124; 4,325,735; 4,330,787; 4,334,234; 4,335,389; 4,336,548; 4,338,611; 4,339,762; and 4,345,262. The basic concept there disclosed is a device having an ink-containing capillary, an orifice plate with an orifice for ejecting ink, and an ink heating mechanism, generally a resistor, in close proximity to the orifice. In operation, the ink heating mechanism is quickly heated, transferring a significant amount of energy to the ink, thereby vaporizing a small portion of the ink and producing a bubble in the capillary. This in turn creates a pressure wave which propels an ink droplet or droplets from the orifice onto a closeby writing surface. By controlling the energy transfer to the ink, the bubble quickly collapses before any ink vapor can escape from the orifice.
In each of the above references, however, the orifice plates disclosed typically provide only orifices and ink capillaries. The rest of the print head is constructed separately to provide independent structures for holding ink for distribution to the capillaries, and hydraulic separation between orifices is provided by having completely separate capillary channels or by constructing independent separators between orifices. None of the above references disclose a one-piece orifice plate having both an ink distribution manifold and hydraulic isolation between orifices or a method of making such an orifice plate which is both precise and inexpensive.